Operations involving the piercing of tissue benefit from control of the velocity of penetration. Tissue is visco-elastic and hence a rapid approach with a cutting instrument is beneficial to prevent tissue from moving away from the penetrator. For example, it is well known to employ scalpels having ultrasound superimposed, in order to cut with very low operator loads and to improve accuracy for initial incision. It would be beneficial therefore to control the velocity of approach of the distal point of a fastener intended for application in soft tissue. This would be particularly true when the configuration of the tissue relative to the screw applicator demands driving the screw away from normal to the tissue plane.
Biologically derived scaffold materials, generally known as extra cellular matrix (ECM), or other types of meshes present a particular challenge for fasteners, because they do not contain through holes for the fastener to pass through making them difficult to penetrate. If the fastener is applied too slowly to the mesh it would likely lead to the mesh material winding up into the threads of the fastener, thereby preventing effective penetration of the fastener. Preferably, the fastener pierces the mesh under rapid rotation and is rotated and advanced through the mesh material before it is distorted or reacts in response to the penetration forces.
Surgical repair of hernias with surgical mesh requires that the mesh be secured with sutures and/or fasteners to assure adequate fixation to the abdominal wall for repair and healing. In repairs such as ventral hernias, the mesh can require numerous fasteners applied using an applicator device with multiple fasteners to achieve the desired apposition of the mesh to the abdominal wall. One such device is an applicator disclosed in U.S. Pat. No. 5,582,616. Applicators of this type rotate the fastener into the mesh and underlying tissue as the surgeon squeezes the handle. The full stroke of the lever must be completed to fully seat the fastener. To achieve full seating of the fastener, the surgeon must oppose the end of the applicator on the exterior abdominal wall of the patient with his free hand, usually for several seconds, while depressing the lever. If the surgeon stops advancing the lever before full stroke, the fastener stops rotating and is not fully seated in the tissue. The surgeon must resume squeezing the lever to finish the fastener application so that it is fully seated. U.S. patent application Ser. No. 12/172,287 described an applicator having an actuator that is capable of storing energy for delivery of a fastener. The actuator is controllable in order to control or interrupt the release of the stored energy. The reference teaches a “dampening means” to control the rate of energy release to a smooth, deliberate action. It does not address the issues related to the delivery of fasteners at slow rates. Thus, during the time it takes to complete the sequence of events to insert a fastener, it is a likely that there would be movement of the applicator tip relative to the fixation site causing the misapplication of the fastener. Other applicators as described in U.S. Pat. No. 5,645,209 employ compressed gas to drive the applicator or as described in U.S. patent application Ser. No. 11/801,507, an electric motor. Although these applicators improve the control and speed of fastener application they require more component parts which add to weight, cost, reliability and shelf life of the devices.
Therefore, there is a need for an device that provides for instantaneous delivery of a surgical fastener with rapid rotational velocity in a reproducible manner without the drawbacks of traditional devices such as compressed air and electric motor devices.